Five coal char samples were burnt in thermobalance with ramp heating rate of 30 K/min. The pore structure of these char samples was studied through mercury intrusion method. Combined with the kinetic theory of gases, ...Five coal char samples were burnt in thermobalance with ramp heating rate of 30 K/min. The pore structure of these char samples was studied through mercury intrusion method. Combined with the kinetic theory of gases, the data of surface area was used in fitting the results. As a result, the kinetic triplet was given. The analysis showed that five char samples share almost the same intrinsic activation energy of the overall reaction. The phenomenological implication of the derived combustion rate equation was given.展开更多
Crystallization is used to produce vast quantities of materials. For several applications, continuous crystallization is often the best operation mode because it is able to reproduce better crystal size distributions ...Crystallization is used to produce vast quantities of materials. For several applications, continuous crystallization is often the best operation mode because it is able to reproduce better crystal size distributions than other operation modes. Nonlinear oscillation in continuous industrial crystallization processes is a well-known phenomenon leading to practical difficulties such that control actions are necessary. Nonlinear oscillation is a consequence of the highly nonlinear kinetics, different feedbacks between the variables and elementary processes taking place in crystallizers units, and the non-equilibrium thermodynamic operation. In this paper the control of a continuous crystallizer model that displays oscillatory behavior is addressed via two practical robust control approaches： （i） modeling error compensation, and （ii） integral high order sliding mode control. The controller designs are based on the reduced-order model representation of the population balance equations resulting after the application of the method of moments. Numerical simulations show good closed-loop performance and robustness properties展开更多
Research on the dynamic properties of a plasma sheath coupled with pitching motion of the vehicle has great significance in solving the problem of communication interruption in the process of vehicle reentry.This pape...Research on the dynamic properties of a plasma sheath coupled with pitching motion of the vehicle has great significance in solving the problem of communication interruption in the process of vehicle reentry.This paper investigates the dynamic properties of the plasma sheath by using the simplified conventional Burnett(SCB)equations and the Navier-Stokes(NS)equations with the thermochemical non-equilibrium effect.The eleven-species chemical kinetic models are applied to the comparison and there is verification of a dynamic plasma sheath simulation for the first time.After the introduction of vehicle pitching motion,the dynamic results are more consistent with the experimental data than the simulated results when treating it as static state.The plasma sheath characteristic parameters show periodic properties,whose changing period is the same as the pitching motion period.However,because of different velocities of the pitching motion,phase shifts exist in different positions of the vehicle.The enhancement of the rarefied effect weakens the disturbance to the plasma sheath.This research reveals the distribution and regularities of the dynamic plasma sheath.It is significant in solving the ionization blackout problem and the design of the reentry vehicle,and provides reliable data for further research on the dynamic plasma sheath.展开更多
基金The work was subsidized by the Special Funds for Major State Basic Research Projects(973).project number G1999022205.
文摘Five coal char samples were burnt in thermobalance with ramp heating rate of 30 K/min. The pore structure of these char samples was studied through mercury intrusion method. Combined with the kinetic theory of gases, the data of surface area was used in fitting the results. As a result, the kinetic triplet was given. The analysis showed that five char samples share almost the same intrinsic activation energy of the overall reaction. The phenomenological implication of the derived combustion rate equation was given.
文摘Crystallization is used to produce vast quantities of materials. For several applications, continuous crystallization is often the best operation mode because it is able to reproduce better crystal size distributions than other operation modes. Nonlinear oscillation in continuous industrial crystallization processes is a well-known phenomenon leading to practical difficulties such that control actions are necessary. Nonlinear oscillation is a consequence of the highly nonlinear kinetics, different feedbacks between the variables and elementary processes taking place in crystallizers units, and the non-equilibrium thermodynamic operation. In this paper the control of a continuous crystallizer model that displays oscillatory behavior is addressed via two practical robust control approaches： （i） modeling error compensation, and （ii） integral high order sliding mode control. The controller designs are based on the reduced-order model representation of the population balance equations resulting after the application of the method of moments. Numerical simulations show good closed-loop performance and robustness properties
文摘Research on the dynamic properties of a plasma sheath coupled with pitching motion of the vehicle has great significance in solving the problem of communication interruption in the process of vehicle reentry.This paper investigates the dynamic properties of the plasma sheath by using the simplified conventional Burnett(SCB)equations and the Navier-Stokes(NS)equations with the thermochemical non-equilibrium effect.The eleven-species chemical kinetic models are applied to the comparison and there is verification of a dynamic plasma sheath simulation for the first time.After the introduction of vehicle pitching motion,the dynamic results are more consistent with the experimental data than the simulated results when treating it as static state.The plasma sheath characteristic parameters show periodic properties,whose changing period is the same as the pitching motion period.However,because of different velocities of the pitching motion,phase shifts exist in different positions of the vehicle.The enhancement of the rarefied effect weakens the disturbance to the plasma sheath.This research reveals the distribution and regularities of the dynamic plasma sheath.It is significant in solving the ionization blackout problem and the design of the reentry vehicle,and provides reliable data for further research on the dynamic plasma sheath.
